scholarly journals Reactivity of chlorine radical with submicron palmitic acid particles: kinetic measurements and product identification

2013 ◽  
Vol 13 (23) ◽  
pp. 11661-11673 ◽  
Author(s):  
M. Mendez ◽  
R. Ciuraru ◽  
S. Gosselin ◽  
S. Batut ◽  
N. Visez ◽  
...  
Keyword(s):  
Palmitic Acid ◽  
Fine Particles ◽  
Reaction Pathway ◽  
Heterogeneous Reaction ◽  
Dicarboxylic Acids ◽  
Uptake Coefficient ◽  
Kinetic Measurements ◽  
Secondary Chemistry ◽  
Ms Analysis ◽  
Tropospheric Aerosol

Abstract. The heterogeneous reaction of Cl• radicals with submicron palmitic acid (PA) particles was studied in an aerosol flow tube in the presence or in the absence of O2. Fine particles were generated by homogeneous condensation of PA vapours and introduced into the reactor, where chlorine atoms were produced by photolysis of Cl2 using UV lamps surrounding the reactor. The effective reactive uptake coefficient (γ) has been determined from the rate loss of PA measured by gas chromatography–mass spectrometer (GC/MS) analysis of reacted particles as a function of the chlorine exposure. In the absence of O2, γ = 14 ± 5 indicates efficient secondary chemistry involving Cl2. GC/MS analysis has shown the formation of monochlorinated and polychlorinated compounds in the oxidized particles. Although the PA particles are solid, the complete mass can be consumed. In the presence of oxygen, the reaction is still dominated by secondary chemistry but the propagation chain length is smaller than in the absence of O2, which leads to an uptake coefficient γ = 3 ± 1. In the particulate phase, oxocarboxylic acids and dicarboxylic acids were identified by GC/MS. The formation of alcohols and monocarboxylic acids is also suspected. A reaction pathway for the main products and more functionalized species is proposed. All these results show that solid organic particles could be efficiently oxidized by gas-phase radicals not only on their surface but also in bulk by mechanisms which are still unclear. They help to understand the aging of primary tropospheric aerosol containing fatty acids.

scholarly journals Reactivity of chlorine radical with submicron palmitic acid particles: kinetic measurements and products identification

2013 ◽  
Vol 13 (6) ◽  
pp. 16925-16960 ◽  
Author(s):  
M. Mendez ◽  
R. Ciuraru ◽  
S. Gosselin ◽  
S. Batut ◽  
N. Visez ◽  
...  
Keyword(s):  
Palmitic Acid ◽  
Fine Particles ◽  
Heterogeneous Reaction ◽  
Dicarboxylic Acids ◽  
Chemical Mechanism ◽  
Reaction Products ◽  
Uptake Coefficient ◽  
Kinetic Measurements ◽  
Secondary Chemistry ◽  
Tropospheric Aerosol

Abstract. The heterogeneous reaction of Cl. radicals with sub-micron palmitic acid (PA) particles was studied in an aerosol flow tube in the presence or in the absence of O2. Fine particles were generated by homogeneous condensation of PA vapors and introduced in the reactor where chlorine atoms are produced by photolysis of Cl2 using UV lamps surrounding the reactor. The effective reactive uptake coefficient (γ) has been determined from the rate loss of PA measured by GC/MS analysis of reacted particles as a function of the chlorine exposure. In the absence of O2, γ = 14 ± 5 indicates efficient secondary chemistry involving Cl2. GC/MS analyses have shown the formation of monochlorinated and polychlorinated compounds in the oxidized particles. Although, the PA particles are solid, the complete mass can be consumed. In the presence of oxygen, the reaction is still dominated by secondary chemistry but the propagation chain length is smaller than in the absence of O2 which leads to an uptake coefficient γ = 3 ± 1. In the particulate phase, oxocarboxylic acids and dicarboxylic acids are identified by GC/MS. Formation of alcohols and monocarboxylic acids are also suspected. All these results show that solid organic particles could be efficiently oxidized by gas-phase radicals not only on their surface, but also in bulk by mechanisms which are still unclear. Furthermore the identified reaction products are explained by a chemical mechanism showing the pathway of the formation of more functionalized products. They help to understand the aging of primary tropospheric aerosol containing fatty acids.

scholarly journals Quantitative GC–MS Analysis of Artificially Aged Paints with Variable Pigment and Linseed Oil Ratios

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2218
Author(s):  
Eliise Tammekivi ◽  
Signe Vahur ◽  
Martin Vilbaste ◽  
Ivo Leito
Keyword(s):  
Palmitic Acid ◽  
Linseed Oil ◽  
Dicarboxylic Acids ◽  
Absolute Quantification ◽  
Substantial Effect ◽  
Pigment Concentration ◽  
Gas Chromatography Mass Spectrometry ◽  
Ms Analysis ◽  
Acid Ratio ◽  
Oil Mixtures

In this study, quantitative gas chromatography–mass spectrometry (GC–MS) analysis was used to evaluate the influence of pigment concentration on the drying of oil paints. Seven sets of artificially aged self-made paints with different pigments (yellow ochre, red ochre, natural cinnabar, zinc white, Prussian blue, chrome oxide green, hematite + kaolinite) and linseed oil mixtures were analysed. In the pigment + linseed oil mixtures, linseed oil concentration varied in the range of 10 to 95 g/100 g. The results demonstrate that the commonly used palmitic acid to stearic acid ratio (P/S) to distinguish between drying oils varied in a vast range (from especially low 0.6 to a common 1.6) even though the paints contained the same linseed oil. Therefore, the P/S ratio is an unreliable parameter, and other criteria should be included for confirmation. The pigment concentration had a substantial effect on the values used to characterise the degree of drying (azelaic acid to palmitic acid ratio (A/P) and the relative content of dicarboxylic acids (∑D)). The absolute quantification showed that almost all oil paint mock-ups were influenced by pigment concentration. Therefore, pigment concentration needs to be considered as another factor when characterising oil-based paint samples based on the lipid profile.

Formation of sodium disulfite in a solid-gas system

1991 ◽  
Vol 56 (8) ◽  
pp. 1575-1579 ◽  
Author(s):  
Jiří Vobiš ◽  
Karel Mocek ◽  
Emerich Erdös
Keyword(s):  
Sodium Sulfite ◽  
Heterogeneous Reaction ◽  
Optimum Conditions ◽  
Kinetic Measurements ◽  
Dissociation Pressure ◽  
Partial Pressures ◽  
Gas System ◽  
Gaseous Sulfur ◽  
Equilibrium Dissociation

The formation of sodium disulfite by the heterogeneous reaction of solid active sodium sulfite with gaseous sulfur dioxide in the presence of water vapour was investigated over the temperature range of 293 to 393 K at SO2. H2O and O2 partial pressures of 1.2-7.4, 1.2-6.4 and 0-11.3 kPa, respectively. The effect of the reaction time was also examined. Kinetic measurements were supplemented with the determination of the equilibrium dissociation pressure of SO2 in contact with sodium sulfite at 373.15 K. The major aim of the work was to establish the optimum conditions for attaining the maximum degree of conversion of the solid reactant to sodium disulfite. The conditions for the formation of virtually pure sodium disulfite were found.

scholarly journals Methanol conversion on borocarbonitride catalysts: Identification and quantification of active sites

2020 ◽  
Vol 6 (26) ◽  
pp. eaba5778 ◽  
Author(s):  
Xuefei Zhang ◽  
Pengqiang Yan ◽  
Junkang Xu ◽  
Fan Li ◽  
Felix Herold ◽  
...  
Keyword(s):  
Active Sites ◽  
Density Functional ◽  
Catalytic Mechanism ◽  
Reaction Pathway ◽  
Methanol Conversion ◽  
Kinetic Measurements ◽  
Catalytic Systems ◽  
X Ray Absorption ◽  
Further Development

Borocarbonitrides (BCNs) have emerged as highly selective catalysts for the oxidative dehydrogenation (ODH) reaction. However, there is a lack of in-depth understanding of the catalytic mechanism over BCN catalysts due to the complexity of the surface oxygen functional groups. Here, BCN nanotubes with multiple active sites are synthesized for oxygen-assisted methanol conversion reaction. The catalyst shows a notable activity improvement for methanol conversion (29%) with excellent selectivity to formaldehyde (54%). Kinetic measurements indicate that carboxylic acid groups on BCN are responsible for the formation of dimethyl ether, while the redox catalysis to formaldehyde occurs on both ketonic carbonyl and boron hydroxyl (B─OH) sites. The ODH reaction pathway on the B─OH site is further revealed by in situ infrared, x-ray absorption spectra, and density functional theory. The present work provides physical-chemical insights into the functional mechanism of BCN catalysts, paving the way for further development of the underexplored nonmetallic catalytic systems.

scholarly journals Study of the heterogeneous reaction of O<sub>3</sub> with CH<sub>3</sub>SCH<sub>3</sub> using the wetted-wall flowtube technique

2003 ◽  
Vol 3 (5) ◽  
pp. 1665-1673 ◽  
Author(s):  
M. Barcellos da Rosa ◽  
W. Behnke ◽  
C. Zetzsch
Keyword(s):  
Ionic Strength ◽  
Aqueous Solutions ◽  
Transport Model ◽  
Heterogeneous Reaction ◽  
Surface Film ◽  
Pure Water ◽  
Order Rate Constant ◽  
Uv Spectrophotometry ◽  
Uptake Coefficient ◽  
Model Calculations

Abstract. This work presents the heterogeneous kinetics of the reaction of CH3SCH3 (dimethyl sulphide, DMS) with O3 (ozone) in aqueous solutions of different ionic strengths (0, 0.1 and 1.0M NaCl) using the wetted-wall flowtube (WWFT) technique. Henry's law coefficients of DMS on pure water and on different concentrations of NaCl (0.1M - 4.0M) in the WWFT from UV spectrophotometric measurements of DMS in the gas phase, using a numerical transport model of phase exchange, were determined to be H ±s (M atm-1) = 2.16±0.5 at 274.4 K, 1.47±0.3 at 283.4 K, 0.72±0.2 at 291 K, 0.57±0.1 at 303.4 K and 0.33±0.1 at 313.4 K on water, on 1.0M NaCl to be H = 1.57±0.4 at 275.7 K, 0.8±0.2 at 291 K and on 4.0M NaCl to be H = 0.44±0.1 at 275.7 K and 0.16±0.04 at 291 K, showing a significant effect of ionic strength, m, on the solubility of DMS according to the equation ln (H/M atm-1) = 4061 T-1 - 0.052 m2 - 50.9 m T-1 - 14.0. At concentrations of DMS(liq) above 50 mM, UV spectrophotometry of both O3(gas) and DMS(gas) enables us to observe simultaneously the reactive uptake of O3 on DMS solution and the gas-liquid equilibration of DMS along the WWFT. The uptake coefficient, g (gamma), of O3 on aqueous solutions of DMS, varying between 1 and 15·10-6, showed a square root-dependence on the aqueous DMS concentration (as expected for diffusive penetration into the surface film, where the reaction takes place in aqueous solution). The uptake coefficient was smaller on NaCl solution in accord with the lower solubility of O3. The heterogeneous reaction of O3(gas) with DMS(liq) was evaluated from the observations of the second order rate constant (kII) for the homogeneous aqueous reaction O3(liq) + DMS(liq) using a numerical model of radial diffusion and reactive penetration, leading to kII ± D kII (in units of 108 M-1 s-1) = 4.1±1.2 at 291.0 K, 2.15±0.65 at 283.4 K and 1.8±0.5 at 274.4 K. Aside from the expected influence on solubility and aqueous-phase diffusion coefficient of both gases there was no significant effect of ionic strength on kII, that was determined for 0.1M NaCl, leading to kII ± D kII (108 M-1 s-1) = 3.2±1.0 at 288 K, 1.7±0.5 at 282 K and 1.3±0.4 at 276 K, and for 1.0M NaCl, leading to 3.2±1.0 at 288 K, 1.3±0.4 at 282 K and 1.2±0.4 at 276 K, where the error limits are estimated from the output of the model calculations, taking the variability of individual runs at various DMS levels into account.

scholarly journals Determination of Dicarboxylic Acids and Levoglucosan in Fine Particles in the Kanto Plain, Japan, for Source Apportionment of Organic Aerosols

2010 ◽  
Vol 10 (3) ◽  
pp. 282-291 ◽  
Author(s):  
Kimiyo Kumagai ◽  
Akihiro Iijima ◽  
Misato Shimoda ◽  
Yoshinori Saitoh ◽  
Kunihisa Kozawa ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Fine Particles ◽  
Organic Aerosols ◽  
Dicarboxylic Acids

scholarly journals Comparative study of the effect of water on the heterogeneous reactions of carbonyl sulfide on the surface of α-Al<sub>2</sub>O<sub>3</sub> and MgO

2009 ◽  
Vol 9 (3) ◽  
pp. 12483-12517
Author(s):  
Y. Liu ◽  
Q. Ma ◽  
H. He
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Heterogeneous Reaction ◽  
Water Vapor Pressure ◽  
Carbonyl Sulfide ◽  
Heterogeneous Reactions ◽  
Uptake Coefficient ◽  
Effect Of Water ◽  
Mineral Dusts ◽  
Α Al2o3

Abstract. The heterogeneous reaction on mineral dust was considered as a new sink of OCS in the troposphere. Here we compared the heterogeneous reactions of carbonyl sulfide (OCS) on the surface of α-Al2O3 and MgO and the effect of water on the reactions at 300 K using Knudsen cell – mass spectrometry, diffuse reflectance infrared Fourier transform spectroscopy, and temperature programmed reactions. H2S and CO2 were found to be hydrolysis products of OCS on both α-Al2O3 and MgO at ambient temperature. At low water vapor pressure, when water vapor pressure in the Knudsen cell reactor increased from 2.3×10−6 to 6.8×10−6 Torr, the initial true uptake coefficient of OCS on α-Al2O3 decreased from 4.70×10−7 to 3.59×10−7; while it increased from 5.19×10−7 to 6.48×10−7 on MgO under the same conditions. At high relative humidity, the observed uptake coefficients of OCS on α-Al2O3 and MgO decreased from 4.63×10−6 to 1.00×10−6 and from 9.72×10−5 to 7.68×10−5, respectively, when RH increased from 0.07 to 0.67 which corresponding to 1.7–15.9 Torr of water vapor pressure. In the RH region of 0.17–0.67, the average observed uptake coefficient of OCS on α-Al2O3 and MgO was equal to 8.34±2.19×10−7 and 8.19±0.48×10−5, respectively. The restrictive effect of water on the heterogeneous reaction of OCS on the surface of α-Al2O3 and MgO was found to be related to competitive adsorption between water and OCS molecules; while the promotive effect of water on the heterogeneous reaction of OCS on the surface of MgO at low coverage was ascribed to the formation of surface hydroxyl groups. When the environmental RH was greater than the RH of the monolayer, which occurred readily at the typical relative humidity of the troposphere, liquid membrane formed on the mineral dusts, especially, the basic liquid membrane formed on the basic component of mineral dusts may be the primary contributor to the heterogeneous hydrolysis of OCS in the troposphere.

scholarly journals Modeling the impact of heterogeneous reactions of chlorine on summertime nitrate formation in Beijing, China

2019 ◽  
Vol 19 (10) ◽  
pp. 6737-6747 ◽  
Author(s):  
Xionghui Qiu ◽  
Qi Ying ◽  
Shuxiao Wang ◽  
Lei Duan ◽  
Jian Zhao ◽  
...  
Keyword(s):  
Heterogeneous Reaction ◽  
Particle Surface ◽  
Heterogeneous Reactions ◽  
Sensitivity Analyses ◽  
Uptake Coefficient ◽  
Transport Models ◽  
Nitrate Concentrations ◽  
The Impact ◽  
Beijing China ◽  
Significant Underestimation

Abstract. Comprehensive chlorine heterogeneous chemistry is incorporated into the Community Multiscale Air Quality (CMAQ) model to evaluate the impact of chlorine-related heterogeneous reaction on diurnal and nocturnal nitrate formation and quantify the nitrate formation from gas-to-particle partitioning of HNO3 and from different heterogeneous pathways. The results show that these heterogeneous reactions increase the atmospheric Cl2 and ClNO2 level (∼ 100 %), which further affects the nitrate formation. Sensitivity analyses of uptake coefficients show that the empirical uptake coefficient for the O3 heterogeneous reaction with chlorinated particles may lead to the large uncertainties in the predicted Cl2 and nitrate concentrations. The N2O5 uptake coefficient with particulate Cl− concentration dependence performs better in capturing the concentration of ClNO2 and nocturnal nitrate concentration. The reaction of OH and NO2 in the daytime increases the nitrate by ∼15 % when the heterogeneous chlorine chemistry is incorporated, resulting in more nitrate formation from HNO3 gas-to-particle partitioning. By contrast, the contribution of the heterogeneous reaction of N2O5 to nitrate concentrations decreases by about 27 % in the nighttime, when its reactions with chlorinated particles are considered. However, the generated gas-phase ClNO2 from the heterogeneous reaction of N2O5 and chlorine-containing particles further reacts with the particle surface to increase the nitrate by 6 %. In general, this study highlights the potential of significant underestimation of daytime concentrations and overestimation of nighttime nitrate concentrations for chemical transport models without proper chlorine chemistry in the gas and particle phases.

Interactions of Calf Spleen Purine Nucleoside Phosphorylase with 8-Azaguanine, and a Bisubstrate Analogue Inhibitor: Implications for the Reaction Mechanism

2004 ◽  
Vol 59 (9-10) ◽  
pp. 713-725 ◽  
Author(s):  
Jacek Wierzchowski ◽  
Agnieszka Bzowska ◽  
Katarzyna Stępniak ◽  
David Shugar
Keyword(s):  
Purine Nucleoside Phosphorylase ◽  
Dissociation Constants ◽  
Reaction Pathway ◽  
Spectral Characteristics ◽  
Difference Spectrum ◽  
Purine Nucleoside ◽  
Fluorimetric Determination ◽  
Kinetic Measurements ◽  
Nucleoside Phosphorylase ◽  
Synthetic Reaction

Abstract Interactions of calf spleen purine nucleoside phosphorylase (PNP) with a non-typical substrate, 8-azaguanine (8-azaG), and a bisubstrate analogue inhibitor, 9-(2-phosphonylmethoxyethyl)- 8-azaguanine (PME-azaG), were investigated by means of steady-state fluorescence spectroscopy. Both 8-azaG and PME-azaG form fluorescent complexes with the enzyme, and dissociation constants are comparable to the appropriate parameters (Km or Ki) obtained from kinetic measurements. PME-azaG inhibits both the phosphorolytic and synthetic pathway of the reaction in a competitive mode. The complex of 8-azaG with PNP is much weaker than the previously reported Gua-PNP complex, and its dissociation constant increases at pH > 7, where 8-azaG exists predominantly as the monoanion (pKa ≈ 6.5). The fluorescence difference spectrum of the PNP/8-azaG complex points to participation of the N(7)H or/and N(8)H tautomers of the neutral substrate, and the 9-(2-phosphonylmethoxyethyl) derivative also exists as a neutral species in the complex with PNP. The latter conclusion is based on spectral characteristics of the PNP/PME-azaG complex, confirmed by fluorimetric determination of dissociation constants, which are virtually pH-independent in the range 6-7. These findings testify to involvement of the neutral purine molecule, and not its monoanion, as the substrate in the reverse, synthetic reaction. It is proposed that, in the reverse reaction pathway, the natural purine substrate is bound to the enzyme as the neutral N(7)H tautomer, which is responsible for the reported strong fluorescence of the guanine-PNP complex.

Sign in / Sign up

Export Citation Format

Share Document